The accurate measurement of the insitu stress states and mechanical properties of the ground media is the most fundamental requirement for proper analysis and sound design of earthen structures, underground openings, dams, foundations, and the like. Such information is also vital in determining the likelihood of failure of critical installations located near fault systems, such as nuclear power generating facilities in the Pacific Rim countries.
Methods and devices have been developed in the prior art to analyze the stress states and material properties of ground media, including pressure meters, hydraulic fracturing devices, and overcoring methods. A complete discussion of the pertinent prior art is provided in U.S. Pat. Nos. 3,796,901, of Mar. 12, 1974, and 4,149,409, of Apr. 17, 1979, both issued to Shosei Serata. In general, the prior art is deficient in that it has not been possible to analyze ground media which is non-homogeneous and does not obey idealized elastic conditions, such as fractured, permeable, non-elastic, or ductile media. Furthermore, the limited data that may be obtained is derived only after extensive laboratory work and data analysis, quite contrary to the ideal goal of virtual real-time measurement of earthen properties and stress states.